Monomer-to-polymer conversion and micro-tensile bond strength to dentine of experimental and commercial adhesives containing diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide or a camphorquinone/amine photo-initiator system

J Dent. 2013 Oct;41(10):918-26. doi: 10.1016/j.jdent.2013.07.007. Epub 2013 Aug 2.


Objectives: To compare the degree of conversion (DC) of adhesives initiated by diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) or a camphorquinone/tertiary amine system (CQ/Amine) as well as their 'immediate' micro-tensile bond strength (μTBS) to bur-cut dentine.

Methods: DC of Scotchbond Universal ('SBU'; 3M ESPE), its experimental counterpart containing TPO as photo-initiator system, an experimental G-aenial Bond ('Ga-B'; GC) adhesive formulation, and an experimental LUB-102 adhesive formulation ('LUB', Kuraray Noritake), containing as photo-initiatior system either 2wt% CQ along with 2wt% tertiary amine ('SBU_CQ/Amine'; 'Ga-B_CQ/Amine'; 'LUB_CQ/Amine'), or 2wt% TPO ('SBU_TPO'; 'Ga-B_TPO'; 'LUB_TPO'), was determined using Fourier-transform infrared spectroscopy (FTIR), after being cured with a dual-wavelength light-curing unit (bluephase 20i, Ivoclar Vivadent). The same adhesive formulations were applied to bur-cut mid-coronal dentine of intact human molars, and subjected to a μTBS test after 1-week water storage. Besides being applied following a self-etch (SE) application mode, the adhesive formulations SBU_CQ/Amine and SBU_TPO were also applied following an etch-and-rinse (E&R) mode, this both for DS and μTBS measurement.

Results: No significant difference in DC was found for any of the adhesive formulations, except for SBU_CQ/Amine_SE and SBU_TPO_SE. For both SBU formulations, a significantly higher DC was reached for the E&R than the SE approach. Regarding μTBS, no significant differences were recorded, except for the significantly higher μTBS measured for SBU_CQ/Amine_E&R and SBU_TPO_E&R.

Conclusions: In self-etch adhesives, the photo-initiator TPO may be used instead of CQ/Amine. The curing and 'immediate' bonding efficiency depended on the application protocol (E&R versus SE), but not on the photo-initiator system.

Clinical significance: The photo-initiator TPO may be used in self-etch adhesives instead of CQ/Amine with similar curing and 'immediate' bonding efficiency.

Keywords: Adhesive; Bond strength; Degree of conversion; Dentine; FTIR; TPO.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Etching, Dental / methods
  • Adult
  • Bisphenol A-Glycidyl Methacrylate / chemistry
  • Camphor / analogs & derivatives*
  • Camphor / chemistry
  • Curing Lights, Dental / classification
  • Dental Bonding*
  • Dentin / ultrastructure*
  • Dentin-Bonding Agents / chemistry*
  • Humans
  • Light-Curing of Dental Adhesives / instrumentation
  • Materials Testing
  • Methacrylates / chemistry
  • Organophosphorus Compounds / chemistry
  • Phosphines / chemistry*
  • Photoinitiators, Dental / chemistry*
  • Polyethylene Glycols / chemistry
  • Polymerization
  • Polymethacrylic Acids / chemistry
  • Resin Cements / chemistry
  • Spectroscopy, Fourier Transform Infrared
  • Stress, Mechanical
  • Tensile Strength
  • Time Factors
  • Water / chemistry
  • Young Adult
  • para-Aminobenzoates / chemistry


  • (2,4,6-trimethylbenzoyl) diphenylphosphine oxide
  • Dentin-Bonding Agents
  • G-Bond
  • MDP adhesion promoting monomer
  • Methacrylates
  • Organophosphorus Compounds
  • Phosphines
  • Photoinitiators, Dental
  • Polymethacrylic Acids
  • Resin Cements
  • ethyl 4-N,N-dimethylaminobenzoate
  • para-Aminobenzoates
  • Water
  • triethylene glycol dimethacrylate
  • Polyethylene Glycols
  • Bisphenol A-Glycidyl Methacrylate
  • hydroxyethyl methacrylate
  • Camphor
  • Scotchbond
  • camphorquinone